This invention relates generally to the field of control circuitry for appliances and more particularly to the use of a single relay in combination with the centrifugal switch of the drive motor for controlling both the drive motor and the heater of a fabric drying machine.
It is well known in the field of microprocessor controlled appliances to utilize relay circuits for energizing various components which operate at different power levels than the microprocessor control. Typically, a separate relay is utilized to perform each function such as energizing dispensers, heaters etc. Since the relays are a relatively expensive portion of the interfacing between the microprocessor control and the various components it is readily apparent that any reduction in the number of relays is beneficial.
U.S. Pat. No. 3,944,841 discusses the use of relay circuitry having two coils and associated with switching apparatus to achieve four control states. Each of the coils is independently energizeable to control different switching combinations for controlling the three dryer loads.
U.S. Pat. No. 4,213,313 discloses relay circuitry which utilizes four relays in different combinations to provide eight operating functions. The disclosure of this patent reveals that a single pole, a double pole and two triple pole relays are used to provide the switching combinations required to achieve these eight functions.
Relay circuitry has thus been shown in the prior art whereby fewer relays are used than the number of functions controlled. There has been no known showing in the prior art of a single relay having a pair of single-pole single-throw switches which cooperate with the centrifugal switch of the drive motor to control energization of the drive motor and the heater or other components responsive to output signals from the microprocessor.